I just keep to the keep it simple attitude. Although you could use a swith on the battery, I see it as a weak point, especially since it has to be good for 25amps or more. What you could do is put a wire out the side of the boat that loops around and back into the boat. Racers use these so they dont chop their arm off when handling an otherwise armed boat. Basically you just run the + wire out the side of the boat and loop it back into a gold plated bullet connector. This imo would be better than a switch.

I dont see a problem with a charger jack. I just thought it was unnecessary.

I would use a deans connector on the motor. Definitely. The whole trick with getting the most power out of your setup, is short thick gauge wire (14 gauge imo) and low resistance connectors. Combined with a low friction drive setup, will give the best efficiency.